Infants born prematurely are at risk for diseases resulting from dysregulation of the acute inflammatory response such as chronic lung disease, overwhelming sepsis and necrotizing enterocolitis (NEC). NEC is a disease of infants born prematurely that commonly leads to significant morbidity or death. While its pathogenesis remains unknown, dysregulation of the acute inflammatory response is implicated. The polymorphonuclear leukocyte (PMN) responds to tissue damage or microbial infection, accomplishing wound surveillance and bacterial containment. The aim of this project is to elucidate regulatory mechanisms governing the PMN response in the acute inflammatory reaction. In adult PMNs, the mammalian target of rapamycin (mTOR) pathway regulates translation of mRNA transcripts with specific 5'- UTR structures. For platelet activating factor (PAF)-stimulated PMNs, translation of interleukin - 6 receptor a (IL-6Ra) and retinoic acid receptor a (RARa) mRNA transcripts is regulated in this manner. Little however, is known regarding the mTOR pathway in neonatal PMNs isolated from healthy term infants or infants born prematurely. We will isolate PMNs from the cord blood of both term and preterm infants and stimulate them with PAF. We will determine both protein expression and phosphorylative activity for each of the components of the mTOR pathway in both cell types. We will then compare the protein expression of both IL-6Ra and RARa in both cell types to their protein expression in adult PMNs. We will also compare IL-6Ra and RARa expression in the PMNs observed in tissue sections of premature infants with NEC to those of infants undergoing abdominal surgery for reasons other than NEC. Finally, we will develop a human PMN development model, differentiating CD34+ hematopoietic stem cells along the granulocytic lineage. Results of these experiments will provide new and important mechanistic insight into the pathogenesis of NEC, and may lead to improvements in the prevention and treatment of this common and often devastating disease of prematurity.